The invention relates, in particular, to a method for reducing the energy consumption of a motor vehicle having an internal combustion engine and at least one vehicle electric system, to which at least a first electric consumer or load is connected.
The number of electric consumers in motor vehicles has increased dramatically. In order to reduce the emission of CO2 in the vehicle, hydraulically operating consumers are being replaced by electric consumers. Thus, for example, one option is to replace the hydraulic steering of the motor vehicle with an electric power steering (EPS). However, such electric consumers can, in a short period of time, overtax the vehicle electric system with their high power demand. The result is that there is also a high demand that the electric system of the motor vehicle be stable. In particular, when high loads occur for a short period of time, adequately high electric voltage or rather electric power must be available.
There is therefore needed, in particular, a method that makes it possible to achieve an efficient vehicle electric system with a reduced energy consumption of a motor vehicle.
This and other needs are met by a method and/or vehicle electric system for reducing the energy consumption of a motor vehicle having an internal combustion engine and at least one vehicle electric system, to which at least a first electric consumer is connected. The internal combustion engine is operated in a first operating mode with a first injection quantity and a first ignition timing. In a second operating mode, the internal combustion engine is operated with a second injection quantity that is higher than the first injection quantity and with a second ignition timing, the second ignition timing at the second injection quantity not being as favorable to the performance of the internal combustion engine as the first ignition timing. In a third operating mode, the internal combustion engine is operated with the second injection quantity and predominantly the first ignition timing so that the performance of the internal combustion engine is higher in the third operating mode than in the second operating mode. A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or the behavior of the vehicle in advance and initiates a switch in the operating modes of the internal combustion engine from the first operating mode to the second operating mode. Advantageous embodiments of the invention are further described herein.
One aspect of the invention consists of the fact that the internal combustion engine is operated in a first operating mode with a first injection quantity and a first ignition timing. For example, both the electric generator of the vehicle and the battery of the vehicle feed jointly the vehicle electric system in order to supply the electric consumers with adequate electric voltage. In the first operating mode the generator can be loaded to full capacity.
In a second operating mode, the internal combustion engine is operated with a second injection quantity that is higher than the first injection quantity and with a second ignition timing. The second ignition timing at the second injection quantity is not as favorable to the performance of the internal combustion engine as the first ignition timing. The second injection quantity that is higher than the first injection quantity increases on its own the performance of the internal combustion engine and enables the internal combustion engine to deliver a higher torque to the electric generator of the motor vehicle. Without any counter-measure, the speed of the internal combustion engine increases—surprisingly to the driver—so that the driver would get the impression that there is a defect. In order to compensate for this rise in torque, the invention provides that in the second operating mode the ignition timing is shifted from the first ignition timing to a second ignition timing. As a result, the performance of the internal combustion engine, or rather its torque, is reduced preferably in essence to the same extent as its torque has been increased by the increase in the injection quantity. The result of the second operating mode is a torque restriction of the internal combustion engine, and the speed of the engine during the transition from the first operating mode to the second operating mode remains largely constant.
In a third operating mode, the internal combustion engine is operated with the second injection quantity and predominantly the first ignition timing so that the performance or rather the torque of the internal combustion engine is higher in the third operating mode than in the second operating mode.
A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or the behavior of the vehicle in advance, and initiates a switch in the operating modes of the internal combustion engine from the first operating mode to the second operating mode. Therefore, the invention provides that the recognition of an imminent specific driving situation causes a torque restriction of the internal combustion engine through an increase in the injection quantity. This torque restriction serves to stabilize the voltage of the vehicle electric system when this voltage is actually required on short notice.
In the known vehicle electric systems of the prior art, turning on an electric consumer that puts a higher load on the vehicle electric system causes a delay in the loading of the electric generator. This delay occurs in that the consumer is fed initially from the vehicle battery and then increasingly by the generator. Typically this procedure, the so-called load-response, lasts a few seconds. Owing to this delay greater fluctuations in the speed of the internal combustion engine upon powering up the consumers with a high current requirement are avoided.
A preferred embodiment of the invention provides that especially in the third operating mode of the internal combustion engine a higher electric load on the vehicle electric system is also largely passed on without delay to the electric generator of the vehicle.
Therefore, this preferred embodiment does not carry out a so-called load-response procedure, in particular, in the third operating mode.
A preferred embodiment of the invention provides that upon recognizing the specific driving situation, the device for detecting the driving situation initiates a switch in the operating modes of the internal combustion engine from the second operating mode to the third operating mode. On account of the inventive torque restriction in the second operating mode, the torque, which is restricted by the internal combustion engine, can be provided on very short notice owing to the displacement of the ignition timing during the transition to the third operating mode. This displacement can be implemented very quickly by way of hardware. The internal combustion engine does not stall and it can deliver the necessary torque to the electric generator. The electric generator can feed a higher electric power into the vehicle electric system and the electric voltage is stabilized, or rather does not collapse, despite a suddenly occurring higher load in the vehicle electric system.
One embodiment of the invention provides that the device for detecting the driving situation recognizes the (actual) occurrence of the specific driving situation by the fact that the electric voltage of the vehicle electric system is on the verge of collapsing. The goal is to monitor the voltage and, if desired, to adjust the ignition angle so as to increase the torque in a relatively simple way with hardware and at a low cost.
One possible embodiment of the invention provides that upon recognizing the imminent specific driving situation, the device for detecting the driving situation initiates, instead of a switch in the operating modes of the internal combustion engine from the first to the second operating mode, a switch in the operating modes of the internal combustion engine directly from the first to the third operating mode.
In this case, it does not concern a preferred, but rather a possible embodiment of the invention.
One embodiment of the invention provides that the device for detecting the driving situation takes into consideration who the current driver is and what his previous behavior has been. In this way the hit rate for predicting that a cornering action is imminent can be raised. If, for example, the device for detecting the driving situation recognizes that the driver in question always swerves during a cornering action (a maneuver that is not always done by every driver), this criterion can be weighted higher in the algorithm for recognizing a cornering action.
One embodiment of the invention provides that the first electric consumer is an electrically operated steering system of the motor vehicle and the imminent specific driving situation is a cornering action. Especially during a cornering action it is important for the driver that the behavior of the steering system not be adversely changed or that the steering not become stiff. During a cornering action the power requirement of an electric steering system is especially high.
One embodiment of the invention provides that the position of the accelerator pedal or rather gas pedal is detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the accelerator pedal or rather the gas pedal is located largely in its rest position, and at least one additional driving situation occurs. Even this feature is a characteristic of an imminent cornering action and yields an important indicator of an imminent cornering action.
A further development of the invention provides that the acceleration and the speed of the vehicle are detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the acceleration of the vehicle is negative, the speed falls below a predetermined threshold value, and at least one additional driving situation occurs. This feature, too, is characteristic of an imminent cornering action and furnishes an important indicator of an imminent cornering action.
A preferred embodiment of the invention provides that the device for detecting the driving situation checks whether the vehicle is making a swerving maneuver. Driving in swerving mode can give a very clear sign of an imminent cornering action.
In one embodiment of the invention the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation. The operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the absolute value of the steering angle is greater than the predetermined threshold value and at least one additional driving situation occurs. This feature may be an indicator that the driver is beginning to make a swerving maneuver or rather a cornering maneuver.
An additional embodiment of the invention provides that the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the absolute value of the steering angle is greater than a predetermined speed-dependent steering threshold or rather steering angle threshold, and at least one additional driving situation occurs. If the driver does not swerve prior to a cornering action, this characteristic of an imminent cornering action may replace the “swerving criterion” and may raise the reliability of the prediction of an imminent cornering action.
A further development of the invention provides that the device for detecting the driving situation checks whether the brake pressure is higher than a predetermined brake pressure or rather a tolerance pressure and, in addition, checks whether the speed is less than a predetermined acceleration-dependent speed value and/or a dynamic cornering threshold. In this way the reliability of the prediction of a cornering action can be increased even more.
In addition, the invention proposes a vehicle electric system of a motor vehicle that exhibits a program-controlled device, which is intended for detecting the driving situation and carries out the method of the invention. Furthermore, the invention proposes a program-controlled device, which is intended for detecting the driving situation and which carries out the method of the invention or initiates its execution.
The inventive method is described in detail below with reference to the flow charts using a cornering action as an example. Identical reference numerals and symbols show the same functions or functions that have the same effect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.